Structure-property relationships of acylated asymmetric dithienophospholes

Friedel-Crafts acylation was found to be an effective way to selectively access mono-functionalized dithienophospholes. Absorption and emission properties of the acylated compounds exhibited high extinction coefficients, relative to unsubstituted dithienophosphole and bathochromic shifts when in the presence of Lewis-acids, e.g., AlCl3 and BF3, effectively demonstrating that the emissive characteristics could be tuned. Subsequent treatment of the asymmetric mono-substituted compounds with N-bromosuccinimide, yielded materials that were later employed in Ni-catalyzed Yamamoto cross-coupling reactions. The resulting cross-coupled material exhibited a substantial increase in its extinction coefficient as well as a further red-shifted absorbance and emission profile, relative to the mono-functionalized phosphole.